/*
 * Copyright 2014 ZXing authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.zxing.client.result;

import java.util.regex.Pattern;

import com.google.zxing.BarcodeFormat;
import com.google.zxing.Result;

/**
 * Detects a result that is likely a vehicle identification number.
 *
 * @author Sean Owen
 */
public final class VINResultParser extends ResultParser {

  private static final Pattern IOQ = Pattern.compile("[IOQ]");
  private static final Pattern AZ09 = Pattern.compile("[A-Z0-9]{17}");

  @Override
  public VINParsedResult parse(Result result) {
    if (result.getBarcodeFormat() != BarcodeFormat.CODE_39) {
      return null;
    }
    String rawText = result.getText();
    rawText = IOQ.matcher(rawText).replaceAll("").trim();
    if (!AZ09.matcher(rawText).matches()) {
      return null;
    }
    try {
      if (!checkChecksum(rawText)) {
        return null;
      }
      String wmi = rawText.substring(0, 3);
      return new VINParsedResult(rawText,
          wmi,
          rawText.substring(3, 9),
          rawText.substring(9, 17),
          countryCode(wmi),
          rawText.substring(3, 8),
          modelYear(rawText.charAt(9)),
          rawText.charAt(10),
          rawText.substring(11));
    } catch (IllegalArgumentException iae) {
      return null;
    }
  }

  private static boolean checkChecksum(CharSequence vin) {
    int sum = 0;
    for (int i = 0; i < vin.length(); i++) {
      sum += vinPositionWeight(i + 1) * vinCharValue(vin.charAt(i));
    }
    char checkChar = vin.charAt(8);
    char expectedCheckChar = checkChar(sum % 11);
    return checkChar == expectedCheckChar;
  }
  
  private static int vinCharValue(char c) {
    if (c >= 'A' && c <= 'I') {
      return (c - 'A') + 1;
    }
    if (c >= 'J' && c <= 'R') {
      return (c - 'J') + 1;
    }
    if (c >= 'S' && c <= 'Z') {
      return (c - 'S') + 2;
    }
    if (c >= '0' && c <= '9') {
      return c - '0';
    }
    throw new IllegalArgumentException();
  }
  
  private static int vinPositionWeight(int position) {
    if (position >= 1 && position <= 7) {
      return 9 - position;
    }
    if (position == 8) {
      return 10;
    }
    if (position == 9) {
      return 0;
    }
    if (position >= 10 && position <= 17) {
      return 19 - position;
    }
    throw new IllegalArgumentException();
  }

  private static char checkChar(int remainder) {
    if (remainder < 10) {
      return (char) ('0' + remainder);
    }
    if (remainder == 10) {
      return 'X';
    }
    throw new IllegalArgumentException();
  }
  
  private static int modelYear(char c) {
    if (c >= 'E' && c <= 'H') {
      return (c - 'E') + 1984;
    }
    if (c >= 'J' && c <= 'N') {
      return (c - 'J') + 1988;
    }
    if (c == 'P') {
      return 1993;
    }
    if (c >= 'R' && c <= 'T') {
      return (c - 'R') + 1994;
    }
    if (c >= 'V' && c <= 'Y') {
      return (c - 'V') + 1997;
    }
    if (c >= '1' && c <= '9') {
      return (c - '1') + 2001;
    }
    if (c >= 'A' && c <= 'D') {
      return (c - 'A') + 2010;
    }
    throw new IllegalArgumentException();
  }

  private static String countryCode(CharSequence wmi) {
    char c1 = wmi.charAt(0);
    char c2 = wmi.charAt(1);
    switch (c1) {
      case '1':
      case '4':
      case '5':
        return "US";
      case '2':
        return "CA";
      case '3':
        if (c2 >= 'A' && c2 <= 'W') {
          return "MX";
        }
        break;
      case '9':
        if ((c2 >= 'A' && c2 <= 'E') || (c2 >= '3' && c2 <= '9')) {
          return "BR";
        }
        break;
      case 'J':
        if (c2 >= 'A' && c2 <= 'T') {
          return "JP";
        }
        break;
      case 'K':
        if (c2 >= 'L' && c2 <= 'R') {
          return "KO";
        }
        break;
      case 'L':
        return "CN";
      case 'M':
        if (c2 >= 'A' && c2 <= 'E') {
          return "IN";
        }
        break;
      case 'S':
        if (c2 >= 'A' && c2 <= 'M') {
          return "UK";
        }
        if (c2 >= 'N' && c2 <= 'T') {
          return "DE";
        }
        break;
      case 'V':
        if (c2 >= 'F' && c2 <= 'R') {
          return "FR";
        }
        if (c2 >= 'S' && c2 <= 'W') {
          return "ES";
        }
        break;
      case 'W':
        return "DE";
      case 'X':
        if (c2 == '0' || (c2 >= '3' && c2 <= '9')) {
          return "RU";
        }
        break;
      case 'Z':
        if (c2 >= 'A' && c2 <= 'R') {
          return "IT";
        }
        break;
    }
    return null;
  }

}
